IMPORTANT ADVICE: If the ambient temperature values are higher than the ones specified above, it should be stated at the ordering stage since these values are taken into account for transformer design and dimensions.

For optimal use of the transformer’s full rating, it is essential that the heat produced by the core and the windings is effectively dissipated.

The installation room must be ventilated well in order to guarantee stable operation and the expected service life of the transformer thanks to natural airflow.

Obstructions around the transformer or close to the enclosure and ventilation openings must be removed.

In order to guarantee standard service conditions and to prevent the transformer from exceeding its temperature limits, it is necessary to install air louvers in the installation room.

The air louvers must be located on 2 opposite walls (one in the bottom part and the other in the upper part) and be sized enough to dissipate the heat generated by the transformer during the service.

Figure 1 – Natural ventilation of the installation room

The minimum size of the openings to guarantee sufficient airflow inside the installation room (considering average annual temperature of 20 C°) can be calculated using the following formulae:


A¹ = lower opening surface (m²)

A²= upper opening surface(m²)

P = total no load losses / load losses at 120° C (kW)

H = difference in height between the top opening and the central line of the transformer (m)

dT = temperature difference between incoming and outcoming air temperature  of the room (C°)

In case the natural ventilation is not sufficient, the louvers may be equipped with fans in order to increase the airflow inside the installation room. In air-conditioned rooms, to avoid water condensation and possible damage of the windings, it is highly recommended not to blow the fresh air directly on the transformer.

 Figure 2 – Forced ventilation of the installation room


  1. Check and respect always the cooling air temperature limits according to the standards and design of your transformers. Our advice list
  2. Don’t blow the fresh air directly on the transformer in air-conditioned rooms! This may cause water condensation on the transformer surface and possible damage of the windings.
  3. Rooms with radiating heat system are not the best place to install your transformer.
  4. Small installation rooms exposed to sunlight and not equipped with additional forced ventilation must be avoided or provided with the correct forced ventilation system.
  5. If the room is poorly ventilated, provide your transformers with cross-flow fans to guarantee the correct removal of heat from the winding channels.